So that the Messenger may warn with it those who are (truly) alive (and so can reason, and see, and hear the truth), and that the word (of Divine judgment after evidence and admonition) may be completed against the unbelievers.

(It has been revealed) so that he (- the Prophet) may warn those who are still (somewhat spiritually) alive (and so capable of receiving and responding to the call of truth), and (that) the verdict (of condemnation) be justified against the disbelievers.

That he or it (Muhammad SAW or the Quran) may give warning to him who is living (a healthy minded the believer), and that Word (charge) may be justified against the disbelievers (dead, as they reject the warnings).

To warn the living and justify the word against the deniers of the reality.

Sayyed Abbas Sadr-Ameli

That it may warn him who is alive and the Word may be proved against the disbelievers.

Al-muntakhab fi tafsir al-Qur'an al-Karim

To use it as the means for a profitable end and to exhort those who are living and spiritually receptive to Allah's commands and to warn those who are spiritually dead to alter their irreverent course of action when warned of its danger, wherefore infidelity shall be justly laid to their charge.